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Q & A: Knocking down a house of cards with light

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Most recent answer: 04/07/2010
Q:
My cousin says that light from a flashlight can knock down a house of cards. Is this true?
- Stephen (age 9)
Denton, Maryland, USA
A:
No, the force from light from an ordinary flashlight is way, way too weak, even for a house of cards.You might be able to do it with a super-mega-laser but you wouldn't want to have one of these around the house.

LeeH

(published on 04/01/2010)

Follow-Up #1: A wave or a particle?

Q:
here when super mega laser knocks down a house of cards ...what is light behaving as ....a wave or a particle..... is it the same in case of photoelectric effect ...(as a particle) .... thanks ....
- Anonymous
A:
Take your pick.  It doesn't make any difference.  In both the classical description of an electromagnetic wave and the quantum photon picture there is momentum carried in the laser beam.  

It is a bit more tricky in the case of the photoelectric effect and the quantum description describes the phenomenon better.  The problem is that there is a minimum energy required to eject a photo-electron  and a classical EM wave whose wavelength is too long just can't do it, no matter what the intensity.  Einstein figured this out.  Check out:    for some information. 

LeeH

(published on 04/07/2010)

Follow-up on this answer.